Transit concrete mixer



1955 H. c. HARBERS ET AL 2,729,435

TRANSIT CONCRETE MIXER Filed Decv 20, 1952 SSheets-Sheet 1 Have) C.H4255es,

0144420 D. .SHAQPE,

INVENTORS ATTORNE).

1956 H. c. HARBERS ET AL 2,729,435

TRANSIT CONCRETE MIXER Filed Dec. 20, 1952 3 Sheets-Sheet 2 OOOOOO HENQYC. 132125525, DWAQD D. HA/QPE, i.) E

IN V EN TORS.

14 TTOQNE Y.

fi H. c. HARBERS ET AL wzww TRANSIT CQNCRETE MIXER Filed Dec. 20, 1952 3Sheets-Sheet 3 fNvExv'roes; LEA/E) C. .IJA-QBERS,

$8 DWAQO D. SHAQPE,

Arrow/vs).

United States PatentO TRANSIT CONCRETE MIXER Henry C. Harbers, Pasadena,and Edward D. Sharpe,

South Pasadena, Calif., assignors to Cook Bros. Equip- ;nent C0., LosAngeles, Calif., a corporation of Caliornra Application December 20,1952, Serial No. 327,092 14 Claims. (Cl. 259172) This invention relatesto transit concrete mixers of the type in which a mixing drum issupported on the rear end of a motor truck and driven in one directionfor charging and mixing concrete therein, and in the reverse directionfor discharging the concrete therefrom.

In such mixers it is highly desirable to drive the drum in eitherdirection through a mechanical mechanism connected to the forward end ofthe truck engine shaft, since such mechanism not only delivers therequisite horsepower to the drum for driving it tomeet all conditions ofcharging, mixing and discharging, but it also enables the drum to bedriven whether the truck ismoving or at a standstill, thereby providingthe particular advantage of discharging concrete from the drum at thejobeither continuously or intermittently, without regard to truck movementwhich is of great value in curb and gutter work.

Such a mechanical drum driving mechanism would have long since gone intogeneral use were it not for the fact that due to the remoteness of thedrum in respect to the front end of the truck engine shaft, themechanism must of necessity consist of many parts which presentmechanical difliculties, and, hence, is prohibitively expensive toconstruct and maintain.

It is, of course, possible to employ a hydraulic mechanism in place ofthe mechanical mechanism and to actuate the former from the forward endof the engine shaft. However, because of the high pressures required ina hydraulic mechanism to drive the drum for all conditions of charging,mixing and discharging, such a mechanism becomes impractical due to thelarge fluid supply required to be carried on the truck, the large andexpensive motor and pump necessary, and the detrimental temperatures towhich the fluid becomes heated because of the high fluid pressuresnecessary to the drums operation.

When a mechanical or hydraulic mechanism of the above described type isemployed, that further important advantage is attained of effectingcontinuous rotation of the drum during transit of the mixerv to a job.In the conventional drum driving mechanism where the power is taken offof the gear transmission, each time the clutch is disengaged and thetransmission moved into neutral incident to stopping forward travel ofthe truck, or when changing gears for different driving speeds, fl1eforce exerted by the weight of the concrete resting on the blades at therising side of the drum, operates to rotate the drum in the reversedirection. Thus when the transmission is again put into gear and theclutch released, sudden stresses 2,729,435 Patented Jan. 3, 1956 licmechanisms to drivingly connect it alone to the drum,

all depending upon the drum driving requirements at any particular time.Thus the driving means of this inven: tion provides the advantages ofboth a hydraulic mechanism and a mechanical mechanism, and thedisadvantages of neither.

It is also a purpose of this invention to provide in conjunction withthe hydraulic mechanism, a mechanism for raising and lowering thedischarge chute of the mixer to eliminate manual actuation thereof.

A further purpose of this invention is to provide in association withthe hydraulic mechanism, an actuating mechanism for a gate to close andopen the discharge end of the drum according as the latter is rotated ina charging and mixing direction, or in a discharging direction.

Only one form of transit concrete mixer will be described herein, andthe novel features thereof pointed out in claims.

In the accompanying drawings:

Fig. l is a view showing in side elevation a transit concrete mixerhaving applied thereto one form of drum driving means, and gate andchute actuating means embodying this invention. I

Fig. 2'is a top plan view of the mixer chassis with the drum drivingmeans, chute actuating means, and gate actuating means applied thereto.

Fig. 3 is an enlarged fragmentary perspective view showing theinterlocking means for the control levers of the invention.

Fig. 4 is an enlarged plan sectional view of the control levers andinterlocking means therefor.

Fig. 5 is a perspective view showing the invention schematically asapplied to those parts of the mixer necessary to its operation. V

Fig. '6 is an enlarged view showing the control valve units of theinvention in horizontal section.

Fig. 7 is a sectional view taken on the line 7--7 of Fig. 6.

Having specific reference to the drawings, the truck mixer shown inFigs. 1 and 2 is conventional in that the rear wheels 15 are driven fromthe engine 16 located at the forward end of the truck, through a clutch17 operatively connecting the rear end of the engine shaft to atransmission 18 of the gear type selectively operable by lever 19 todrive a shaft 20 which extends rearwardly and is operatively connectedto the rear wheels through a difierential 21.

Supported on the rear end of the truck frame for rotation about aninclined axis, is a mixing drum 22 having an open upper rear end throughwhich the drum is adapted to be charged with concrete, mixed or unmixed,from a hopper 23 supported on a frame 24 fixed on the truck frame. Thedrum 22 is provided interiorly with spiral blades 25 shown in brokenlines in Fig. 1, and under rotation of the drum in one direction theseblades operate to feed the concrete inwardly from the open end of thedrum as it is fed thereto by the hopper 23, and also to agitate theconcrete and prevent setting thereof during transit of the truck to ajob. When the drum is rotated in the other direction the concrete isdischarged from the rear end of the drum into a chute 26. To preventaccidental discharge of concrete from the drum during transit of thetruck to a job, its rear end is partly closed bya gate 27 whichisadapted to beopened to permit concrete to be discharged from the drum.

This invention consists in the main of two driving mechanisms for thedrum 22, one'a hydraulic mechanism, and the other amechanical'mechanism, and both of which are actuated by the engine 16.The hydraulic mechanism comprises a rotary pump 28 driven from afrontend extension 29; of the engine shaft, through a chain and sprocketconnection 30. Fluid is supplied to the pump 28 by a'feed line'31connectedto a fluidsupply tank '32, and fluid under pressure isdischarged from the pump through a pressure line 33 whichextends'rearwardiy of the truck to a valve unit 34. As will be describedlater herein,'the valve unit 34 is connected to a second valve unit 35,and the latteris'connected to the tank32 through a'return line 36.

The valve unit 35 directionally controls the circulation of pressurefiuid from the pump 28 to'and from a fiuid motor 37 through lines '38and 39. The motor 37 is of the conventional rotary gear type, and onegear thereof is fixed to a shaft 40 for driving 'the latter. 'From thisshaft 40 motion is transmitted to a transverse shaft 41 through suitablegearing 42', and theshaft 41,in'turn, is operatively connected to athirdshaft 43 through suitablegearing 44'. The shaft 43-is operativelyconnected to the forwardend of the'drum 22 through a chain and sprocket-connection'45. These several elements, notincluding the motor 37,constitute a drum rotating mechanism which is adapted to be driveneither by the motor or the mechanical mechanism of this invention tobelater described herein, and, hence, such rotating mechanism is common toboth the hydraulic mechanism and the mechanical mechanism.

The valve unit 34 is provided for thepurpose of controlling the supplyofpressure fluid to a conventional ram 46 comprising acylinder 47 and apiston 48, the fluid being delivered and returned from the cylinder ateither sideof the piston by pipes 49 and 50. As shown in- Fig. 1, oneend of the cylinder 47 is mounted on the rear end of the truck by aswivel connection 51-so that it 'can be moved verticallyand-horizontallythe rod 48a of the piston 48 pivotally-connectedas at 52 to the chute.The chute 26:is.swivelly mounted'on the rear end of thetruck,.as.-indicated at 26a, sothat it can-be adjusted horizontally aswell as vertically to discharge concrete to any point desired withinthe-range ofadjustment provided'by the swivel mounting.

Thevalve unit 34 comprises a valvehousing 53 in the longitudinal bore53a of which is a spool valve 54 movable .axially by a lever 55 tooccupy a neutral position and either of two extreme positions. As bestshown in Fig. 6, the housing 53 is provided with aninlet port '55a towhich connects the pressure line 33 to the bore 53a. The. housing.5 3 isalso providedwith two passageways 56 at one side of the bore 53a, and athird passageway 57 at; the,other sideofthe bore. At the same side ofthe bore as the passageway 57 are two upwardly extending passageways 58and 58a connected respectively to the lines 49 and 50.

The valve unit 35 likewise comprises a housing 59 in the. longitudinalbore 59a of which is a spool valve 60 operable by a lever 61 to occupy aneutral position and either of two extreme positions. This housing 59 isprovided with a passageway 62 which, through a port 63 is connected tothe passageway 57 of the unit 34, At the other side of the bore 59a apair of upwardly extending passageways 64 and 64a are provided andpositioned upon opposite side of a horizontal passageway 65. Throughaport 66 this passageway is placed in communication with the return line36. The passageways 64 and 64a lead from the bore 59a to the lines 38.and 39, respectively, in order that fluid can be supplied .to themotor'37 in either direction from the pressure line.33 under thecontrol, of course, of the valve 60, and .returned to the tank 32through the line 36.

Included in thehydraulic mechanism is a fluid-means for opening andclosing the gate 27, that comprises a ram 67 which, as shown in Figs. 1and 5, has the piston rod 67a thereof operatively connected to an arm 68pivoted as at 69 on the frame 24, and secured to the gate 27 so thataccording as the piston is moved upwardly or downwardly the gate willbeclosed or opened. Pressure fluid is supplied to and returned from theram 67 by lines 70 and 70:: connected respectively to the lines 38 and39 so that depending upon the direction of fluid supply to the pump 37the gate will be opened or closed, as will be more fully describedhereinafter.

As will be seen in Figs. 1 and 2, the valve units 34 and 35 are situatedat the rear end of the truck in order that the operator, while standingin an observing position at the rear of the truck, can, through thelevers 55 and 61, manipulate the valves 54 and 60 to control thedeliveryof pressure fluid from the pump 28 to the motor 37' andthe ram 46particularly to eliect discharge of concrete from the drum at the job,and to adjust the chute 26 vertically to discharge the concrete at anydesired elevation.

As an additional actuating means for the valve 60, a second controllever 71 is situated in the cab of the truclnpivoted as at 72, andoperatively connected to the lever 61 by rods 73 and 74 and a bell-cranklever 75. This lever 71 enables the driver of the truck, while seated inthe cab, to operate the valve 60, while in position to operate the lever19 and the clutch 17 to effect forward movement of the truck as and whennecessary.

The mechanical drum driving mechanism of this invention comprises aconventional power take-otf unit generally indicated at 76, and havingthe drive gears 77 thereof (see Fig. 5) operated by the driving gears ofthe transmission 18, and driven gears 78 splined on the forward end ofthe shaft '49. The gears 78 are, by a lever 79 pivoted as at 80,shiftable from a neutral position to a forward position in which theshaft 40 drives the drum 22 through theintermediate mechanism, in adirection for charging the drum with concrete and mixing thereof. Thelever 70 is also movable to a reverse position in which the shaft 40 isreversely driven to drive the drum '22 in the other direction todischarge concrete therefrom.

Since the shaft 40 can be driven in either direction by the unit 76 orthe motor 37, it is necessary to provide some means which will preventthe unit from being connected to the shaft to drive it in a directionopposed to the direction in which it is being driven by the motor. Forthis purpose a latch is provided comprising a stationary keeper 81'formed on a plate 82, and a U-shaped latch member 83 pivoted as at 84 onthe lever 79so as to be movable from the position shown in Fig.3 to thatshown in Fig. 4. In the Fig. 3 position the member 83 engages thekeeper81 to lock the lever 79 against movementin either direction'from aneutral position. In the position shown in Fig. 4 the member 83 locksthe levers 79 and 71 to each other so that .movement of either levereffects corresponding movement of the other lever. It will, of course,be understood that both levers must be in neutral position before thelatch member can be moved to the lever interlocking position shown inFig. 4. While the levers 71 and 79 are shown in Fig. 5 ashaving separatepivots 72 and 80, in practice'they have a common pivot in the form of apin 85 with its ends fixed inthe plate 82 and a second plate 86,as-shown in Figs. 3 and 4.

The operation of the invention is as follows:

To charge the drum with concrete from a source situated above thehopper23, it is first necessary to set the druminto rotation in a forwarddirection, that is, counterclockwise as when viewedin Fig. 5, so thattheconcreteisjfedforwardly in the drum under the action of the blades25. During this charging operation the concrete fiows into the rear endof the drum at a point above the gate 27, it being understood that thegate is mater closed during this operation. If the concrete is premixedthen it is only necessary to drive the drum at a relatively low speed,and to do so the hydraulic mecl1anism alone provides the necessary powerfor the purpose.

Normally the two valves 54 and 60 occupy the neutral positions shown inFig. 6 so that fluid from the pressure line 33 is free to circulatethrough" the valves and their housings 53 and 59 back to the tank 32. Inthe neutral position of the valve 54 the passageways 58 are closed toblock fluid in the ram cylinder 47. To set the motor 37 into operationfor driving the drum 22 in the direction required for charging, thevalve 60 is moved to an extreme position in which pressure fluid fromthe bore 59a can pass through that passageway 64 into the line 39, fluidfrom the discharge side of the motor returning to the line 36 throughthe line 38, passageway 64a, bore 59a, and passageway 65; t

The lever 61 and 71 being interconnected as described, the valve 60 canbe moved to the aforesaid'extreme position by either lever, but thelatch member" 83 must be first swung clear of the lever 71 to theposition shown in Fig. 3. In this position of the latch member the lever79 is locked in neutral position so that it cannot be accidentally movedto set the mechanical mechanism into operation in opposition to themotor 37.

With pressure fluid circulating through the motor 37 in the directionabove described such fluid is also supplied to the ram 67 and in suchdirection as to maintain the gate 27 in closed position.

If the drum is being charged with concrete that has not been premixed,the drum must be rotated at a greater speed to effect proper mixingthereof, thus requiring greater power than can be developed by thehydraulic mechanism alone. Therefore, to drive theldrum as required, themechanical mechanism is now employed to assist the hydraulic mechanism.The mechanical mechanism can be set into operation by first restoringthe lever 71 to neutral position whereupon, the latch member 83 is swungto the position shown in Fig. 4 so as to interlock the levers 71 and 79.By now moving either lever forwardly the two levers are moved together,the lever 71 moving the valve 60 to the aforedescribed position forcirculating pressure fluid through the motor 37 to rotate the drum in aforward direction, and the lever 79 shifting the power take-off unit 76to drive the shaft 40 in the same direction as driven by' themotor;Accordingly, mechanical and hydraulic mechanisms are coupled one to theother to drive the drum at the required speed for thorough mixing of theunmixed concrete with which the drum is being charged.

Once the drum has been charged with pro-mixed concrete or unmixedconcrete and the latter thoroughly mixed in the drum, the truck is readyto travel to the job, butsince during such travel it is only necessaryto drive the drum at a relatively low speed so as to keep the concretetherein agitated to prevent setting thereof, the mechanical mechanismmay be disconnected from the shaft 40 and only the hydraulic mechanismmaintained in operation. To accomplish this the levers 71 and 79 arefirst restored to neutral position whereupon, the latch member 83 isswung to the position shown in Fig. 3 to lock the lever 79 in neutralposition and free the lever 71 for independent operation. The lever 71is now moved to actuate the valve 60 so as toset the motor the case inmost instances, it can be accomplished by the hydraulic mechanism alone.To do this the. lever 61 is actuated by the operator while standing atthe rear end of the truck in a position to move the chute 26 iQfllCdesired horizontal position, and to also actuate the lever for loweringand elevating thechute to position the V .6 discharge end thereof at therequired elevation for a particularjob. 1 1 'I- Actuation of thelever-61 is such as' to move the valve 60 to the other extreme positionwherein pressure fluid from the bore 59a can pass to the passageway64aand from the latter to line 38 to drive the motor-'37 in the oppositedirection to that previously driven so as to drive the drum in a reversedirection and discharge concrete therefrom into the chute. It will beunderstood that the fluid as discharged from the motor is returnedto'the tank 32 through line 39, passageway 64, bore 59a, passageway 65,port 66, and line 36.

To permit concrete discharge from the drum, the gate 27, of course, hasto be opened, and this is eflected automatically" and simultaneously'With driving of the motor 37, since part of the pressure fluid flowingto the motor 37 passes into the line 70 and thence to the cylinder 47 atthe top side of the piston 48.

.To operate the ram 46 for adjusting the chute 26 vertically, the valve54 is moved by the lever 55 from neutral position to one extremeposition or'the other, depending upon whether it is desired to raiseorlower the chute. To raise the chute the valve 54 is moved to thatextreme position necessary to place the passageway 58 in communicationwith the bore 53a so that pressure fluid from the bore will flow to thelower end of the ram cylinder 47 through the line 49. Fluid from theupper end of the cylinder 47 is returned by the line 50 to thepassageway 58a and finally to the return line 36 through the valve unit35 as will be obvious from a consideration of Fig. 6. Manifestly,movement of the valve 54 to the other extrerne position eifectscirculation of the fluid in the opposite direction to that effected forraising the chute, and thus the ram 46 is made operable to lower thechute.

It is important to note that the construction of the valves 54 and 60,middle arrangement of ports and passageways in the housings 53 and 59are such that irrespective of the position of the valve 54, fluid canpass to the housing 59 for operation of the motor 37 in either direction as controlled by adjustment of the valve 60.

From the foregoing operation of the hydraulic mechanism to rotate thedrum 22 for concrete discharge, it will be apparent that such dischargeis possible irrespective of whether the truck is moving or at astandstill, since the pump 28 is at all times driven by the engine 16.This is of great advantage in pouring concrete for curb and gutter work.

If a job requires a rapid'rate of concrete pouring, naturally therotational speed of the drum must be increased beyond that possible bythe hydraulic mechanism. Therefore, it is necessary to resort to themechanical mechanism to assist the hydraulic mechanism to that end.'Accordingly, .the power take-off unit 76 is now drivingly connected tothe shaft 40 by first restoring the lever 71 to neutral position todiscontinue operation of the motor 37 and allow interlocking of thelever with the lever 79,

so that when the lever 79 is moved to reverse position to effect reversedriving of the drum, the lever 71 will likewise be moved to reverseposition causing the motor 37 to be driven by the-pressure fluid in thesame direction as the unit 76 drives the shaft 40. This insures the twomechanisms driving the shaft 40 in the same direction, and thus preventsthe two mechanisms opposing each other and mutilating the gears andother parts of the mechanisms.

Although only one form of transit concrete mixer is shown and describedherein, it is to be understood that various changes and modifications ofthe mechanical drum driving means and the hydraulic drum driving meansas well as the controls therefor, may be made herein without departingfrom the spirit of the invention and the spirit and scope of theappended claims.

What is claimed is: a 1. In a transit concrete mixer: a truck; an enginefor propelling the truck; a transmission mechanism; a drum rotatablymounted on the truck; mechanical means con- .nected loathe-transmissionmechanism; thydraulic means connected to the-forwardend-of-the engineshaft; afirst controltmeans for the mechanical meansselectivelyoperable-to connect thelatter tothe drumcto drive .the same in eitherdirection; a second control means .for the hydraulic means selectivelyoperable toconnect the latter to thedrum to drive thesame in eitherdirection; 'and a means movable toone positionin which it interlocks'thetwo control means toeach other for simultaneous operation, and anotherposition in whichthe first control means vis-locked'againstoperation-andthe second control means released for-operation.

2.- In a transit concrete mixer: .a truck; 'an engine-for propelling thetruck; a transmission mechanism; a-drum rotatably mounted -on.the-rtruck; mechanical means connected to the transmission mechanismand including a snafu-hydraulic means connected to the shaft of saidengine and including a motor; "a first control means for the mechanicalmeans selectively operable to connect the latter to the drum to drivethe same in either direction; a second control means for the hydraulicmeans selectively operable to connect the motor to the drum to drive thesame in either direction; and a latching device manuallytmovable to oneposition in-which it interlocks the two control means with each otherfor simultaneous operation to causethe mechanical means to assist thehydraulic means in driving said drum, and anotherposition in which thefirst control means is locked-against operation and the second controlmeans released for operation.

3. In a transit concrete mixer: a truckyan engine for propelling thetruck; a selective transmission for drivingly able to drive saidmechanism ineither direction; hydraulic means permanently connected tothe shaft of said engine and including a motor drivingly connected tosaid mechanism, and a valve selectively operable to cause the motor todrive said mechanism in either direction; and means so controllingactuation of the valve and said unit that both of said means can beconnected to said mechanism -to drive the latter simultaneously in onedirection orthe other.

4. Means for driving the drum of. a transit' concrete .mixer fr'omthetruck engine, including: a selective power 'takc-oif unit; a hydraulicpump adapted to be constantly driven by said engine; a hydraulic motorselectively driven in either direction by said pump; mechanismoperatively connecting the drum-to said motor and "said unit; a firstmeans controlling directional operation of said'motor; a

second means controlling directional operation of said unit; and athirdmeans'for so controlling operation of the first-and second means thatsaid-unit andsaid motor can be caused to drivesaid.mechanismsimultaneously in one direction or the other, or the motoralone in'either direc tion.

5. in a transitmixer: a truck; an 'engine;:: drum rotatably mounted onthe truck and having an open rear end; a. gate'for'closing said end; ahydraulic system in- -cluding asourceof fluid, aipump connected to saidsource and drivingly connectedto the-engine, a'motor operated by thepump and drivingly connected to the-drum, a ram for-closing and openingthe gate, and a valve selectively controlling circulation of pressurefluid from the pump to the'motor and return to said source in eitherdirection, and simultaneously-from'the pump to the ram and return tosaid source 'in' 'either direction, so that according as "tltedi'umis'rotated in 'onedirection or the otherby'the motorfthe ram will 'be"operated to close or open'the gate.

6. In 'a"transitmixer: a truck; an engine; a selective "transmissiomfordrivingly conneeting'the engine to the truck; a'fdrumrotatablymounted'onLthe truck and having an. open rear end; a gate'for closingsaid end; a chute stvivelly mounted at the, rear end of the truck; arotating mechanism for the drum; ahydraulic circuit including a sourceofifluirl, .a :purnppermanently driven by theen- .ginc, a motoroperatively connected to said mechanism, a ram foractuating the gate, asecond ram for raising and lowering the chute; a valve for directionallycontrollling the circulation of pressure fluid from the pump tothemotordn eitherldirectionand itsreturn to-said source, andsimultaneously .to thegaterani in either'direction and its returnto'saidsource,so that according as the drum .isrrotatedinone direction or theother, thegate ram will be simultaneously operated to close or open-thegate; and a second valve for controlling the circulation ofpressure'fiuid from the pump to .thesecond ram in either direction andits return to said source.

7. In .a transitmixer: a truck; an engine; a selective transmissionfordrivingly connecting the engine to the truck; a drumrotatably mountedon the .truckandihaving an open vrear .end; agate forclosing vsaid end;a chute swivelly mounted at the reartcndofthe truck; arotating mechanismfor thedrum; .a hydraulic circuitincludinga source of fluid, a .pumppermanently driven-by the en- :gine, a motoroperatively connected tosaid mechanism, a ram for actuating .thegate, a second ramtor raisingandloweringthemhute; avalve for directionally controlling thecirculation of pressure .fiuid from the pump to the motor ineither-direction, and its returnto said source,

and simultaneously to the. gate ram in either direction and its returnto said source, so that according as the drum is rotated-inoneadirectionor the other, the gate ram will operatettoclose or'open-thegate; a'second'valve-for controllingthe-circulation ofpressurefluid from the pumpto the second ramin either direction and'itsreturn to said sourcepsaid valves having fluidpassagcs so-arrangedrelatively' that the second valvecan be actuated to raise or lower thechute without interfering with circulation of fluid toand .from themotor in either direction.

8. Means for driving the drum of a transit concrete mixer-from 'thetruck engine, including: a selective power take-oft unit;-a=hydraulicpump adapted to be constantly dri-ven bysaid-engine;ahydraulic motorselectively driven tiirection,--or saidzmotor alone inteither direction.

9. -.In a transit concrete mixer: 21 truck;.an engines-for cpropellingthe itruckya selective transmission for drivingly connectingdhe engineto-the .rear'wheels of ;the:.truck;?a adru'm rotatably mounted on thetruck; drum rotating mechanism; :mechahicalmeans connected to saidtransmission and including a'p'ower take-oft unit selectively'operable'ito' drive said mechanism-in either direction;

hydraulicmeans permanently'connected to'the shaft of saiden'gineandiincluding a motor drivingly connected to 'said mechanism, anda-valve movable from a-neutral position to'eith'er oftwo extremepositions for causing "the motor-todrive said-'mechanism-in e'itherdirection; a

first lever for actuating the valve; :1 second lever-movablefrom'a'neutral position to either of two extreme positions for causingsaid unit to drive said mechanism in either direction; and a latchingdevice having a stationary keeper and a latch member pivoted on thesecond lever to occupy one position in which it interlocks the twolevers. for

simultaneous operation to occupy the same extreme vpositions, andanother position in whichlit engages the keeper to lock" the second ilevertin i neutral position, and

frees the'firstlever 'for operation.

10. In a transit mixer as embodied in claim 1, wherein the drum has anopen rear end; a gate for closing said end; a hydraulic ram for closingand opening the gate; and means so interconnecting the hydraulic means,said ram, and the second control means that according as the latter isoperated to connect the hydraulic means to the drum to drive the same inone direction or the other the ram will be operated to open or close thegate.

11. In a transit concrete mixer: a truck; an engine for propelling thetruck; a transmission; a drum rotatably mounted on the truck; amechanism operatively con nected to the drum for driving the same;hydraulic means continuously driven by the engine and selectivelyconnectabie to the mechanism for driving the latter in either direction;mechanical means connected to the transmission and selectively operableto assist the hydraulic means in driving the mechanism in eitherdirection; and manually operable means so controlling operation of themechanical means and the hydraulic means that the two can be caused tosimultaneously drive the mechanism in one direction or the other, or thehydraulic means alone.

12. In a transit concrete mixer: a drum; a first driving means for thedrum of relatively low horse power; a second driving means for the drumof relatively high horse power; a first means to operatively connect thefirst driving means to the drum so as to rotate the latter in eitherdirection; a second means to operatively connect the second drivingmeans to the drum to rotate the latter in either direction; means toconnect the first and second means to each other for simultaneousoperation to couple both driving means to the drum for driving thereofin the same direction; and means operable to lock the second drivingmeans in a non-connecting position when the second driving means is in acorresponding position.

13. In a transit concrete mixer: a truck; an engine for propelling thetruck; a transmission mechanism; a drum rotatably mounted on the truck;mechanical means connected to the transmission mechanism; a hydraulicmotor; a first control means for the mechanical means selectivelyoperable to connect the latter to the drum to drive the same in eitherdirection; a second control means for said motor selectively operable toconnect the latter to the drum to drive the same in either direction;and means permanently connecting said motor to the engine shaft forconstant driving thereby so that the drum can be driven by said motorthrough operation of the second control means whether the truck is inmotion or at a standstill.

14. In a transit concrete mixer: a drum; a first driving means for thedrum of relatively low horsepower; a second driving means for the drumof relatively high horsepower; a first means to operatively connect thefirst driving means to the drum so as to rotate the latter in eitherdirection; a second means to operatively connect the second drivingmeans to the drum to rotate the latter in either direction; and meansselectively operable to connect the first and second means to each otherfor simultaneous operation to couple both driving means to the drum fordriving thereof in one direction or the other, or by the first meansalone in one direction or the other.

References Cited in the file of this patent UNITED STATES PATENTS1,036,743 Suudh Aug. 27, 1912 1,232,605 Raddatz July 10, 1917 1,349,924Swanson Aug. 17, 1920 1,867,838 Jaeger July 19, 1932 2,510,858 BlackJune 6, 1950

